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Red-Eared Slider Lighting: The Ultimate Guide

Aquarium lighting is an important aspect of keeping any aquatic creature. 

For red-eared sliders, it is absolutely essential for their health to provide the right type and amount of light. 

In this guide, we are discussing the different types of aquarium lighting and how to light a red-eared slider tank properly.

3 Reasons Red-Eared Sliders Need Light

Red-eared sliders rely on light for their physical health and to facilitate natural behaviors. There are four key benefits of light to pet turtles:

  1. UVB absorption
  2. Natural photoperiod
  3. Basking behaviors
  4. Communication


UVB radiation is essential for red-eared sliders to absorb calcium properly. This helps prevent metabolic bone disease, a common health issue in pet turtles. Turtles cannot convert vitamin D into its active form for calcium absorption without UVB light.[1]

UVB radiation for Red-Eared Slider Lighting


A natural photoperiod simulates the day/night cycle that red-eared sliders experience in the wild. This is important for their overall health and well-being. A 12-hour day/night cycle is ideal.

A natural photoperiod signals to turtles when to exhibit certain behaviors such as eating and basking during the day and resting at night. An improper photoperiod can impact your red-eared sliders’ sleep and affect their growth and immune system.

Related: How Big Do Red-Eared Sliders Get?


Basking is a natural behavior of red-eared sliders. They bask to regulate their body temperature and absorb UVB radiation. Basking also helps them dry off their shell, which is vital for shell health.

Basking takes up the majority of a wild red-eared slider’s day. The lack of opportunity to exhibit this natural behavior in captivity can cause both physical and mental health problems.

Red-Eared Slider basking
Image Source


Human eyes cannot see UV rays, but red-eared sliders have a different vision. They can visibly see UV rays. This spectrum and its reflection help them communicate with each other. 

For example, it’s theorized that UV rays reflect coloration in males, attracting females.[2]

Improper lighting may also impact their ability to communicate and reproduce.

What Lamps Do Red-Eared Sliders Need?

A red-eared slider enclosure needs three different lights to create the perfect lighting and environment: UVB lighting, heat lighting, and daylight.


A UVB light is the most important type of light for red-eared sliders. It helps them to absorb calcium and vitamin D properly.[3]


A heat lamp creates a basking spot for your turtle. The basking spot should be around 85-88°F. Red-eared sliders are ectotherms and rely on basking to regulate their body temperature.


A “daylight” lamp or regular light bulb can create more ambient light in the tank if the UVB lamp does not emit enough light to fill the tank. This is not a necessary light but can help create a more natural environment for your turtle.

How Much Light Do Red-Eared Sliders Need?

Red-eared sliders need at least 12 hours of light every day. This is because they need to bask for many hours every day. Light and basking help keep them healthy.

Basking is so essential to turtles’ overall health that they can become stressed without it. This can lead to a suppressed immune system and a shorter lifespan.

Red-eared sliders also need periods of darkness to digest their food and rest properly. 

As a result, it’s crucial to provide your red-eared slider with a basking habitat with both a basking platform and a hiding spot. This way they can regulate their temperature and get the light they need and a natural light schedule.

How Much Light Do Red-Eared Sliders Need
Image Source

Red-Eared Slider Light Schedule

It’s important to balance light and dark, encourage a natural photoperiod, and support restful sleep[4]. Your turtle should have access to light for 12-14 hours each day.

To create this schedule, simply turn off the tank lamps each night and back on again in the morning. This includes the heat source, as a temperature drop is normal overnight.

Many owners invest in a timer that can automatically turn on and off lights to ensure a consistent schedule.

Do Red-Eared Sliders Need Light At Night?

You may have heard that you should keep a night light on for your red-eared slider, but this is not true. These turtles are diurnal and prefer to sleep in the dark.

Exposure to light at night can disrupt their sleeping patterns and cause stress. If you must keep a light on in the room where your turtle lives, cover the tank with a towel or sheet to block the light.

UVB Light For Red-Eared Sliders

UVB light is essential for the red-eared slider to regulate the synthesis of Vitamin D3. This vitamin is vital as it allows turtles to absorb and use calcium. Without UVB light, turtles eventually develop Metabolic Bone Disease.

Metabolic bone disease (MBD) is a condition that results in deformities and weak bones. It can be fatal if left untreated.[5]

Various UVB light sources are available on the market to offer indoor pet turtles vital UVB light. When choosing a light for your pet, be sure to select one that emits the correct wavelength of UVB light.

UVB Light For Red-Eared Sliders

Types of UVB Lamps

When choosing an aquarium lighting system, you have two main options:

  1. Tube lights
  2. Compact fluorescents

Compact fluorescents are more energy-efficient and hardly take up any space. There is speculation that direct rays from compact fluorescents may contribute to the development of photo-kerato-conjunctivitis, but many owners have used them for years with no issues. 

Either way, use a reflector around the bulb to reduce the risk of eye damage.

Tube lights are generally safer but are more expensive, and you need to mount them on the tank. They also cover more of the tank than compact fluorescents.

UVB Bulb Placement

Place the UV bulb at the end of the tank above the basking spot. This placement creates a gradient so your turtle can get away from the UV rays and self-regulate its intake.

Mount the UV bulb inside the tank with no barriers, such as glass or mesh, between the lamp and the basking spot.

The bulb should also be close enough to your turtle so they can benefit from the UVB rays, but not so close that it scorches them.

Position the UV lamp so that the basking spot is 3.0-4.0 on the UV index. Measure the UVI by using a solar meter. UV light dissipates through the air, so the further away from the basking spot you place the lamp, the less UVB light reaches it.

UVB Bulb Placement
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UVB Lamp Replacement

One of the unfortunate things about UVB bulbs is that they need to be replaced every 6 to 8 months. As they age, their spectrum gradually shifts out of the optimal output. So although a year-old bulb may look perfectly fine, it isn’t delivering any vital light that turtles need.

It may seem excessive to buy a new light every six months, but it’s just one of the necessary costs of owning a turtle. By replacing your UVB bulb regularly, you ensure that your turtle gets the light it needs to stay healthy and thrive.

You can monitor the UV bulb’s output by measuring it regularly with a solar meter. This way, you can replace the bulb as it wears out, which may be a little longer than six months.

Basking Light Wattage

Baskings lights come in all different wattages, and it can be confusing to choose the right one. A good rule of thumb is to use a light with 50 watts per square foot of basking area.

For example, if your basking spot is 12” by 12” or 144 square inches, you would need a bulb of at least 72 watts.

Generally, the wattage does not matter if the basking area is within the correct UVI. Position a high wattage bulb higher and lower wattage closer to the basking area.

Basking Light Wattage
Image Source

How Much UVB Do Red-Eared Sliders Need?

Red-eared sliders are Ferguson Zone 3-4, which means they are open or mid-day sun baskers that appreciate strong sunlight. The recommended UVI for this species is between 3.0 and 4.0 in the basking area. 

While all turtles need access to UV rays, it is especially important for red-eared sliders during their first few years[6]. This is when they grow the fastest and need UV light to synthesize vitamin D3 properly. 

Without this vitamin, their bones do not develop properly, and they can become severely stunted.

As adults, red-eared sliders can go without UV light for extended periods, as they typically brumate during cold weather. They still need regular access to UV to maintain their health in captivity.


Can I Use A Regular Light Bulb For My Red-Eared Slider?

A regular bulb can create some natural daylight within the tank but is not suitable on its own. Regular bulbs do not emit vital UVB red-eared sliders.

Can I Put My Turtle In The Sun?

Yes, you can put your turtle in the sun but only on warm days and for short periods. Their tank should not be positioned in the sun as the glass can create high temperatures and block UV rays.

How Often Should I Change My UVB Bulb?

Change UVB bulbs every six months to ensure that your turtle gets the right amount of light.

How Do I Know If My UVB Bulb Is Working?

You can use a solar meter to measure the output of your UVB bulb and make sure it is in the correct range.

What Happens If Red-Eared Sliders Don’t Get Light?

If red-eared sliders don’t get light, they can experience many health problems, such as shell problems, skin problems, and eye problems.

About Sophie Herlihy (Zoologist)

Sophie Herlihy, a trained zoologist, is a lover of true misfit animals. With a specialty in insects, birds, and rodents, she helps the Misfit Animals craft factual and valuable informational pieces on various animals.

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